Preheat the oven to 350°F and line a baking sheet with parchment paper.
Drizzle the chicken with 1 tablespoon olive oil and toss to coat. Sprinkle over the Cajun seasoning, ensuring the chicken is evenly coated.
In a skillet over medium heat, add 2 tablespoons olive oil (or enough to coat the bottom of the pan). Cook chicken for about 4-5 minutes, flip once, reduce heat to low, and continue to cook for another 3-4 minutes, or until cooked through. Transfer the chicken to a cutting board and set aside while you make the sauce.
In the same pan, reduce the heat to medium-low and add 2 tablespoons of butter to melt. Add the garlic and sauté until fragrant. Pour in the heavy cream, add Cajun seasoning, and stir. Bring to a low simmer until it begins to thicken, about 5 minutes. Add the parmesan cheese and stir until melted. Taste and adjust seasoning if needed, then set aside.
In a bowl, combine the softened butter, minced garlic, red pepper flakes (if using), and parsley. Microwave for 5-10 seconds to partially melt the butter.
Slice the bread in half lengthwise and spread the garlic butter evenly on both halves. Bake in the oven for 5-10 minutes until partially toasted.
While the bread is toasting, slice the chicken into bite-sized pieces.
Top the bread with cheese and chicken, dividing evenly between both sides. Layer half the cheese first, then the chicken, and finish with the remaining cheese.
Drizzle about ⅓ cup of alfredo sauce over each piece of bread. Bake for another 5-10 minutes, or until the cheese has melted and the edges of the bread are golden brown. Optionally, broil for 1-2 minutes to achieve a toasted and bubbly cheese topping.
Slice into 2-inch pieces and serve with the remaining alfredo sauce for dipping.